Mechanical apparatus



March 1, 1966 S NT N 3,237,255,

- MECHANICAL APPARATUS I Original Filed Dec. 12, 1958 OUENCH TANK ' nus UP INVENTOR. E0556 7 JrAA/fm ATTORNEY United States Fatent O 3,237,255 MECHANICAL APPARATUS Robert L. Stanton, Maplewood, N .J assignor to American Manufacturing Company, Inc., a corporation of Delaware Original application Dec. 12, 1958, Ser. No. 780,107. Divided and this application Sept. 27, 1962, Ser. No.

6 Claims. (Cl. 24-16) This application is a division of my co-pending application Serial No. 780,107 filed December 12, 1958 and entitled, Banding Strip and Method for the Manufacture Thereof, now abandoned.

This invention relates to securing means for strip material used for the binding of packages and more particularly to clips or seals for strapping or banding material made from plastics.

Steel banding or strapping is commonly used to encompass and retain a plurality of objects and in packaging of heavy objects to protect the shipping container from breakage or damage. Such banding is usually made of inexpensive cold rolled steel strip, the free ends of which are secured by means of a clip and has proven to be an excellent means of protecting high density packages from damage and destruction in shipping.

The steel bands heretofore employed have several drawbacks. The use of steel strapping can add significantly to the weight of the package. In addition, sharp bends in the steel material tend to weaken it at the point of flexure so that not infrequently, bands will snap in the course of shipment. Another major disadvantage lies in the fact that the metal used is subject to corrosion and the corrosion products may disfigure the container and possibly damage the contents. Still another problem arises from the possibility of injury during the removal of the sharp edged steel from the package due to difficulties encountered in such removal particularly in the absence of proper tools.

In view of these and other objectives, substitutes have been sought for the steel banding strip which would retain the advantages of the banding and overcome the objections stated above. To this end, other materials including special cords and various types of fiber reinforced plastic strips or tapes have been tried, but hitherto, none of the substitutes proposed have met with outstanding success because of high cost, inconvenience in use or manufacture, and difficulty in securing the banding strip to the package.

It is an object of this invention to provide for low cost plastic banding strips, a securing means therefor which can be easily applied to packages and which can perform as well or better than steel banding under the abuse encountered in shipment and storage of the packages to which it is applied.

This and other objects, benefits and advantages will become apparent from the following description and in conjunction with the accompanying drawings and claims:

FIGURE 1 is a perspective view of a securing clip in accordance with the present invention as applied to a plastic banding strip for packages;

FIGURE 2 is a plan view of a fragment of the banding material;

FIGURE 3 is a cross-section of the banding strip shown in FIGURE 2 taken along line 3-3 thereof;

FIGURE 4 is a perspective view of a clip in accordance with the present invention, used to secure the bending strip as it appears before crimping;

FIGURE 5 is an enlarged plan view of the clip as it appears after being clinched about the ends of the banding strip;

FIGURE 6 is a cross-section of the clipped band taken "ice along line 66 of FIGURE 5 shown on an enlarged scale; and

FIGURE 7 is a view of the extrusion arrangement embodying a process for forming, stretching and orienting the plastic strip with which this invention may be used.

As may be seen from FIGURES 1, 2 and 3, the strapping or banding strip 11 consists of an elongated band of material which may be applied to bundles or packages in the same manner as currently commercially available steel banding strip material. A suitable length of the strip material is wrapped around and encompasses the desired article or group of articles which may or may not have been previously enclosed in a wrapper or container. Thus, by way of example, the strapping 11 as shown is applied to the package 10. Conventional banding tools may be employed for stretching the band so that it tightly encompasses the package. The free ends of the strip 11 are secured by means of clip 12. The strip 11 is of substantially the same proportions in terms of width and thickness as the steel banding presently in general use.

The clip element 12 is particularly adapted for use in conjunction with the banding strip 11. Said clip comprises a channel-shaped element of generally U-shaped cross-section having a web portion 14 from which leg portions 15 extend. The leg portions 15 are initially directed at an acute angle with respect to the plane of the web so that they may be more readily clinched inwardly and toward the web. In clinching the clip, the free ends of the strip 11 are disposed within the channel portion of the clip and by use of a suitable clinching tool not shown, the leg portions 15 are folded inwardly and against the undersurface of the strip while simultaneously a series of transverse crimps or corrugations 16 are simultaneously impressed upon the flattened clip. As a consequence of this, and as may be more clearly seen in FIG- URES 5 and 6, the entire clip as well as the strip ends disposed therein are formed into a series of sinuous convolutions or corrugations which serve to firmly grip and retain the free ends of the strip against displacement without damaging the strip itself or subjecting it to any action which may cause deterioration in the ability of the strip to withstand the strains encountered in use.

The banding strip 11 is advantageously formed by the extrusion process. FIGURE 7 illustrates the general extrusion arrangement whereby this is accomplished. As may be seen in FIGURE 7, an extruder 17 which may be of conventional form, is equipped with a hopper 18 into which the plastic material, to be more particularly hereinafter described, is fed in pellet form. The extruder 17 melts the plastic material and expresses it through die section 19 which has a suitable die disposed therein provided with an opening in the desired shape for the formation of a strip 11 as shown in FIGURE 3. As the strip is conveyed away from the extrusion machine by means of the pull-off arrangement, to be more particularly described, it is passed through a quench tank or similar arrangement 20 which subjects the strip to a cooling action and stabilizes it for further processing. In order to form the banding strip 11, only partial cooling is accomplished in the quench tank 20 and the strip thus partially cooled as by being passed through a bath of water at room temperature, is pulled by means of the orienting and stretching device designated generally by the numeral 29 so that the strip is stretched and oriented in order to impart to it the desired characteristics and to yield a sufficiently high strength material suitable for use as a banding strip. The stretching and orientation of the strip is accomplished by rotating the orienting and stretching rolls 21 of the orienting device 19 at a speed in excess of the rotational speed of the pull-off rolls 22 and in the same direction. The strip material is subjected to a temperature below its softening point during this operation. For this purpose, a suitable heating arrangement is provided in the region of the two pairs of rolls and therebetween.

The plastic, polypropylene, which is a high molecular weight polymer of propylene with an ordered isotactic structure having a molecular weight in the range of 10,000 to 200,000 is a particularly useful material for the formation of the banding strip of the present invention. There are a number of materials of this type commercially available at the present time. Among them are the Moplen material made by the Montecatini Company of Italy and Profax material made by the Hercules Powder Company of Wilmington, Delaware. These materials when extruded and oriented by the method herein described result in a strip of properties particularly suitable for handing use. The product of the herein described process results in a highly fibrous structure and is flexible so that it is capable of conforming to the shapes desired in packaging.

Polypropylene strip material in the form herein employed has highly desirable characteristics which add materially to the strength of the band or strap. It is not subject to stress relaxation as are many other plastic materials and hence the tension applied to the band is maintained indefinitely. There is thus eliminated the tendency to creep present in other plastic materials whereby in time the tension on the band drops to a fraction of the original value. The polypropylene strip formed as herein described has a much lower elastic modulus in tension and in flexure which means that the extent to which the material may be stretched to achieve a given level of tension in the band is much greater thereby permitting better control of the banding operation. The lower modulus in flexure is the property which permits the material to bend easily and to conform to the shape of a package without causing large localized stress concentrations of the type that lead to premature failure often encountered in steel banding strip.

Among the other advantages of the polypropylene material is its low specific gravity of 0.90, which makes it competitive with steel on a cost basis since the ultimate tensile strength is about the same as low carbon steel and it has about the specific weight. The strip is extruded with smooth edges and hence the danger of accidental injury is reduced. The material has less tendency to mar or scratch finished surfaces if the banding is applied directly to certain items. Furthermore, the material is highly resistant to the normally encountered environments. It will not corrode, and is resistant to mildew and to many of the commonly encountered chemicals such as acids and alkalis.

The extrusion temperature for polypropylene, the preferred material of the present invention, is approximately 400 F. at the die. The material is allowed to cool in a room temperature water bath before it passes through the pull-off rolls. The rates of speed of the pull-off device and orienting device are adjusted so that the material is elongated between the range of 6 to 10 times its initial length while the material is maintained at a temperature between 250 F. and 300 F. The elongation ratio of from 6:1 to 10:1 results in a draw down ratio of from 2 /211 to 3:1.

The very high degree of orientation obtained by this elongation process converts the strip to what is in effect a cemented bundle of long fibers. The elongation and orientation raises the tensile strength of the strip to the same levels that would be expected of twisted strand of highly oriented fibers of the plastic material. Since polypropylene exhibits the property of having almost a completely elastic response in tensile loading, i.e.: the material obeys Hookes law that the stress is proportional to the strain, it will make a good tensile member and will maintain tension around a package to which it is applied.

This in contrast to the response of many other plastic materials which have a high degree of visco-elastic response and will initially show a high stress level which falls rapidly with time and in addition show a high level viscous response which is commonly referred to as cold flow. The alteration of the strip to this fibrous structure by the orientation process is not visually apparent and the strip retains the convenience, handling ability and appearance of a flat tape while providing the physical characteristics of a highly oriented multifibrous structure.

I have here shown and described a preferred embodiment of my invention. It will be apparent, however, that this invention is not limited to this embodiment, and that many changes, additions and modifications can be made in connection therewith without departing from the spirit and scope of the invention as herein disclosed and hereafter claimed.

I claim:

1. A clip for strapping material made of a single band of smooth plastic material comprising: a metal element having two substantially planar leg portions respectively joined to opposite sides of a substantially planar and rectangular intermediate portion, said leg portions being folded inwardly toward one another around overlapping portions of said band and being disposed substantially parallel to said intermediate portion and said overlapping band portions, said leg and intermediate portions having formed therein a plurality of corrugations which is substantially transverse to the longitudinal axis of said tape, the respective depths of said corrugations being at least a multiple of an integer other than one of the thickness of said band.

2. The clip according to claim 1 wherein the thickness of said clip is substantially uniform at all points thereon.

3. A clip assembly for strapping material consisting essentially of a single flat band of highly-oriented polypropylene, said clip comprising: a metal element having two substantially planar leg portions respectively joined to opposite sides of a substantially planar and rectangular intermediate portion, said leg portions being folded inwardly toward one another around overlapped portions of said band and being disposed substantially parallel to said intermediate portion and said overlapped portions, said leg and intermediate portions and the overlapped band portions enfolded therein having formed therein a plurality of transverse corrugations extending across said clip substantially from one of said sides of said intermediate portion to the other, said sides remaining unbroken and rectilinear despite said corrugations.

4. The clip according to claim 3 wherein said corrugations are characterized by at least three troughs.

5. A clip for strapping material consisting essentially of a single band of highly-oriented polypropylene comprising: a metal element having two substantially planar and rectangular leg portions respectively joined to opposite sides of a substantially rectangular and planar intermediate web portion, said leg portions being folded inwardly toward one another to enclose overlapping portions of said hand, said overlapping portions being portions wherein an under face of one band portion contacts an upper face of another band portion, said leg portions also being disposed substantially parallel to said intermediate web portion and said overlapping portions, said leg and intermediate web portions and said overlapped band portions having formed therein a plurality of transverse corrugations which do not break the surfaces of said clip and extend across said clip substantially from one of said sides to the other, said corrugations having a depth which is at least a multiple of an integer other than one of the thickness of said band, the projections of said sides being substantially rectilinear despite said corrugations, said corrugations being respectively uniform in depth throughout their lengths.

6. The clip according to claim 5 wherein the distances throughout.

References Cited by the Examiner UNITED STATES PATENTS Rothermel 24123 Depew 2423 Kimball et a1. 2423 Harvey 2420 King 2423 6 Johnson 2423 Rebichon et a1. 2423 Ott 2423 Humphner 2423 Karass 2416 X Wyckofi et a1. 2416 WILLIAM FELDMAN, Primary Examiner.

ABRAHAM G. STONE, DONLEY J. STOCKING,

Examiners.

P. A. TAUCHER, D. L. BURGESS, Assistant Examiners. 

1. A CLIP FOR STRAPPING MATERIAL MADE OF A SINGLE BAND OF SMOOTH PLASTIC MATERIAL COMPRISING: A METAL ELEMENT HAVING TWO SUBSTANTIALLY PLANAR LEG PORTIONS RESPECTIVELY JOINED TO OPPOSITE SIDES OF A SUBSTANTIALLY PLANAR AND RECTANGULAR INTERMEDIATE PORTION, SAID LEG PORTIONS, BEING FOLDED INWARDLY TOWARD ONE ANOTHER AROUND OVERLAPPING PORTIONS OF SAID BAND AND BEING DISPISED SUSBTANTIALLY PARALLEL TO SAID INTERMEDIATE PORTION AND SAID OVERLAPPING BAND PORTIONS, SAID LEG AND INTERMEDIATE PORTIONS HAVING FORMED THEREIN A PLURALITY OF CORRUGATIONS WHICH IS SUBSTANTIALLY TRANSVERSE TO THE LONGITUDINAL AXIS OF SAID TAPS, THE RESPECTIVE DEPTHS OF SAID CORRUGATIONS BEING AT LEAST A MULTIPLE OF AN INTEGER OTHER ONE OF THE THICKNESS OF SAID BAND. 